Impact of environmental factors on the variability of the avian dawn chorus

Abstract

The avian dawn chorus is especially prominent during the spring and summer when birds are breeding. The short-term and seasonal variation (timing, level, duration, and spectrum) of the avian dawn chorus is not well understood, and this study represents an initial effort to correlate changes in different chorus characteristics with different environmental variables. Acoustical data were gathered with a Larson Davis Sound Level Meter at the U.S. Fish and Wildlife Service Bear River Migratory Bird Refuge from March through August 2021 and 2022 and were analyzed for variation in start time and acoustical characteristics. Although it has been shown that the chorus start time is roughly correlated with civil twilight, we found that they ranged from 3 h before nautical twilight to half an hour after. Additionally, daily maximum SPL during a dawn chorus can vary during the peak breeding season by more than 40 dB. We analyzed the effect of several environmental variables on the dawn chorus, including nearby water levels, cloud coverage, wind, etc., as well as overall seasonal variation. Our findings highlight the importance of water and demonstrate the need for continued research and analysis of daily variation. Results will be discussed.